Question

What is the best/ideal interval between COVID-19 vaccine doses?

4 January 2021. Related: All topics, COVID-19.

Answer

Answer: Simon Collins

In the UK, NHS guidelines recommendations are slightly different for each vaccine. 

• The second dose of the Pfizer/BioNTech vaccine can be given from 3 to 12 weeks after the first dose.
• The second dose of the AstraZeneca/Oxford vaccine can be given from 4 to 12 weeks after the first dose.

In practice, both vaccines are now being given with 12 weeks between doses. There is no choice for which vaccine you get or the timing of doses.

However, these recommendations have been made based on limited evidence, some of which is not publicly available. Pfizer, for example, only supports a three week dosing interval based on lack of evidence for anything longer, even though the NHS has extended this to 12 weeks. The limited information about the longer dosing of the Oxford vaccine came from the UK study using the half-dose (which is not being given).

Individual protection will be better when the second dose is given earlier – i.e. after either 3 or 4 weeks. This is because full protection will be reached more quickly.

On a population level, government policy is to try to give the first dose to as many people as possible. This is looking at reducing risk for the UK as a whole given limited access to vaccines. The policy also recommends that the same vaccine should be used for both doses.

The first dose of either vaccine will give a good level of protection. Other vaccines have shown that giving the second dose later can be better than giving it too early.

The real answer is that there is not enough evidence to answer this question.

For more information please see this PDF:
https://www.england.nhs.uk/coronavirus/wp-content/uploads/sites/52/2020/12/C0994-System-letter-COVID-19-vaccination-deployment-planning-30-December-2020.pdf

This is one of more than 60 questions about COVID vaccines. It was produced by and for people living with HIV.

See also:
Q&A on COVID vaccines: are they safe and effective?